Thanks to these commands, I’ve founded out we had CentOS 5, with 64 bits (x86_64 with “uname -i”, for examle).

Afterthat, to keep safe the server, I’ve installed yum-priorites following this CentOS HowTo:

yum install yum-priorities

Then, we make sure yum-priorities is enabled by looking at /etc/yum/pluginconf.d/priorities.conf :

enabled=1

Now we have yum-priorities installed and enabled, so now we edit /etc/yum.repos.d repositories adding this line:

priority=N

where N equals 1 on [base], [addons], [updates] and [extras] modules, equals 2 on [centoplus] and [contrib], and equals 10 on new repositories we’ll add later.

Now we have to add Dag’s rpmforge repository, where ffmpeg will be downloaded from. First, we download the rpm according to our distribution and architecture, in this case, CentOS 5 and x86_64. Second, we import Dag’s GPG key. Third, we verify the downloaded package. And fourth, we install the rpm: